Mach Tornado is the name of Meta Knight's Standard Special Move. The tornado also appears to be significantly larger than the Mario Tornado, Dr. Tornado, and Luigi Cyclone. It appears to be based on one of Meta Knight's attacks from various Kirby games. The move's inertia carries Meta Knight left and right (depending on which direction you put) and Meta Knight rises when you push the B button. In a video posted outside of the Dojo, we see mostly how this attack works. It appears to last for about 3 seconds, with Meta Knight being free to move while performing the attack. If a opponent is caught in its hitbox and that Meta-Knight doesn't change direction, the foe cannot DI out of it.
If B is rapidly pushed while Meta Knight is using the Mach Tornado, he will gain altitude. In addition, the tornado will last longer.